Process for production of hydrocarbon liquids and gases from oil shale

ABSTRACT

A process for the production of hydrocarbon liquids and gases from oil shale comprising the steps of gradually preheating oil shale in a preheat and prehydrogenation zone to a temperature of about 700* to about 950*F. in the presence of hydrogen-rich gas without substantial production of liquid and gas in the preheat and prehydrogenation zone, then destructively distilling the preheated and prehydrogenated oil shale in a hydroretort zone at a temperature of about 850* to about 1,250*F. in the presence of hydrogen-rich gas to form aliphatic and alicyclic hydrocarbon liquids and low molecular weight paraffinic hydrocarbon gases from the preheated and prehydrogenated organic hydrocarbon portion of the oil shale. The hydrogen-rich gas may be passed countercurrent in thermal exchange relation to the spent shale to recover heat from the spent shale heating the hydrogen-rich gas for passage countercurrent and in thermal exchange relation to fresh oil shale in the preheat and prehydrogenation zone. The improvement of this process lies in the exceptionally high conversion of the organic component of oil shale to products of high value including high yields of readily distillable liquids comprising a high proportion of aliphatic and alicyclic hydrocarbon liquids and to low molecular weight paraffinic hydrocarbon gases. The process can be controlled, if desired, to maximize production of aliphatic and alicyclic hydrocarbon liquids. The liquids produced by this invention may be utilized for a wide variety of purposes including gasification for the production of synthetic pipeline-quality gas from oil shale.

United States Patent Linden et al.

in] 3,922,215 Nov. 25, 1975 1 PROCESS FOR PRODUCTION OF HYDROCARBONLIQUlDS AND GASES FROM OIL SHALE [75] Inventors: Henry R. Linden,Chicago; Paul B.

Tarman, Elmliurst; Harlan L. Feldkirchner, Elk Grove Village, all of111.

[73] Assignee: American Gas Association,

Arlington, Va.

[22] Filed: June 1, 1973 [21] Appl. No.: 365,973

[52] US. Cl. 208/11; 48/197 R [51] Int. Cl. C10B 53/06 [58] Field ofSearch 208/11; 48/197 R [56] References Cited UNITED STATES PATENTS1,833.155 11/1931 Danner et al... 208/11 2,639,982 5/1953 Kalbach 208/112,991,164 7/1961 Elliott at al. 48/197 R 3,224,954 12/1965 Schlinger etal. 208/11 3,421,868 1/1969 Feldman 208/11 3,484,364 12/1969 Hemminger208/11 3,703,052 11/1972 Linden 48/197 R Primary ExaminerC. DavisAttorney, Agent, or Firm-Thomas W. Speckman and gases from oil shalecomprising the steps of gradually preheating oil shale in a preheat andprehydrogenation zone to a temperature of about 700 to about 950F. inthe presence of hydrogen-rich gas without substantial production ofliquid and gas in the preheat and prehydrogenation zone, thendestructively distilling the preheated and prehydrogenated oil shale ina hydroretort zone at a temperature of about 850 to about 1,250F. in thepresence of hydrogen-rich gas to form aliphatic and alicyclichydrocarbon liquids and low molecular weight paraffinic hydrocarbongases from the preheated and prehydrogenated organic hydrocarbon portionof 'theoil shale. The hydrogen-rich gas may be passed countercurrent inthermal exchange relation to the spen't shale to recover heat from thespent shale heating the hydrogen-rich gas for passage countercurrent andin thermal exchange relation to fresh oil shale in the. preheat andprehydrogenation zone. The improvement of this process lies in theexceptionally high conversion of the organic component of oil shale toproducts of high value including high yields of readily distillableliquids comprising a high proportion of aliphatic and alicyclichydrocarbon liquids and to low molecular weight paraffinic hydrocarbongases. The process can be controlled, if desired, to maximize productionof aliphatic and alicyclic hydrocarbon liquids. The liquids produced bythis invention may be utilized for a wide variety of purposes includinggasification for the production of synthetic pipeline-quality gas fromoil shale.

U.S. Patent Nov.25, 1975 Sheet10f2 3,922,215

I fiifi 0/2 I V 5M5 I l l l l I I l I I I I US. Patent Nov. 25, 1975Sheet 2 of2 3,922,215

PROCESS FOR PRODUCTION OF HYDROCARBON LIQUIDS AND GASES FROM OIL SHALEThis invention relates to an improved process for the production ofaliphatic and alicyclic hydrocarbon liquids and low molecular weightparaffinic gases from oil shales. Aliphatic hydrocarbons include open,straight or branched chain molecules which may be saturated orunsaturated. Alicyclic hydrocarbons are cyclic molecules substantiallyfree from aromatic double bonds. Low molecular weight paraffinichydrocarbon gases include molecules of 4 and less carbon atoms, namelymethane, ethane, propane, butane and isobutane. The aliphatic andalicyclic hydrocarbon liquids produced by the process of this inventionare especially suited for various further processing. One important useof such liquids is preparing a high methane content pipelinequality gassuitable as a substitute for or as a supplement to natural gas. Otherimportant uses of such hydrocarbon liquids include production ofnaphtha, gasoline, kerosine, jet fuel, diesel oil and light fuel oils,and other low boiling distillate oils.

Oil shales are sedimentary rocks which are thought to have been formedfrom finely divided mineral matter and organic debris from aquaticorganisms and some plant matter which were deposited on the bottoms ofshallow lakes and seas and later solidified. The resulting oil shalesare fine-grained impermeable rocks in which it is almost impossible toseparate the organic component and the inorganic mineral matter withoutchanging the structure of the organic component. The largest inorganicconstituent of oil shales are carbonates. Oil shales vary in the amountand in the constitution of the organic component which is calledkerogen. Typical oil shales contain about to weight percent kerogen.Kerogen is a high molecular weight hydrocarbon having a molecular weightof over 3000 and a carbon to hydrogen weight ratio (C/H) typically ofabout 7/1 to 8/1.

Due to the high demands upon natural gas supplies and their limitedreserves, synthetic pipeline gas will be needed to supplement suchnatural gas in the United States and other countries of the world. Theinterest in an economical process for producing synthetic pipeline gasfrom oil shales is high. There are abundant reserves of commercialgrades of oil shales in the United States, particularly in thenorthwestern areas of Colorado and adjoining areas of Utah and Wyoming.

To be suitable as use for pipeline gas, the heating value must be about900 to 1 100 BTU/SCF which results from high methane content, normally80 percent by volume or greater. Such specifications require that forpipeline-quality gas the carbon to hydrogen weight ratio be low,approaching as low as 3/1.

To produce a high yield of valuable hydrocarbons from oil shales, it isdesirable to limit the coking and aromatization of the oil shalesorganic component and to maximize the production of low-boilingaliphatic and alicyclic hydrocarbon liquids from the oil shales. Infurther processing such hydrocarbons, in turn, give the highest yieldsof valuable liquid products or fuel gases and cause the least formationof high-boiling aromatic oils and carbon or coke during gasification. Itis also desired in the production of desired quality hydrocarbons fromoil shales, to limit decomposition of mineral carbonates present in theoil shale and resultant carbon dioxide formation which increases processheat require- 2 merits, consumption of hydrogen, and greatly increasesthe difficulty of further processing Previous processes for theproduction of hydrocarbon fuels from oil shale have the disadvantages oflower thermal efficiency and/or lower conversion of the organiccomponent oil shale to suitable gas or readily gasifiable liquids.

It is an object of this invention to optimize the production ofaliphatic and alicyclic hydrocarbon liquids and paraffinic hydrocarbongases from oil shale suitable for further processing.

It is another object of this invention to provide a process for theproduction of aliphatic and alicyclic hydrocarbon liquids and lowmolecular weight paraffinic hydrocarbon gases from oil shale wherein theoil shale is preheated and prehydrogenated by countercurrent flow ofhydrogen-rich gas and may be hydroretorted by countercurrent orcocurrent flow of hydrogen-rich gas.

It is still another object of this invention to provide a process forhigh yield production of pipeline-quality gas from oil shale by aprocess characterized by its high thermal efficiency.

Further objects of this invention will appear to one skilled in the artas this description proceeds and by reference to the figures.

Preferred embodiments of this invention are illustrated in the drawingswherein:

FIG. 1 is a block flow diagram illustrating the production ofhydrocarbon liquids from oil shale using one embodimentof the process ofthis invention; and

FIG. 2 is a block diagram showing the production of pipeline-quality gasfrom oil shale by one embodiment of this invention.

The process of this invention is applicable to a wide variety of oilshales. For high efficiency it is desired that the Fischer Assay, whichindicates the oil yield obtained by conventional retorting of the oilshale, be 25 gallons per ton or more. However, the process of thisinvention is also applicable to oil shales having lower Fischer Assays,down to about 10 gallons per ton.

The size of the shale particles used in the process of this invention isnot important, but particles generally of the size 1/16 inch to 1 inchdiameter are utilized. Use

of very fine particle shales may give difficulty in clogging duringprocessing and large particle shales have a lower surface area and mayresult in longer processing times.

The fresh oil shale is fed into a preheat and prehydrogenation zone andgradually preheated to a temperature of about 700 about 950F. in thepresence of hydrogen-rich gas. It is preferred that the temperature towhich the oil shale is heated in the preheat and prehydrogenation zoneis about 750 to about 850F. At 700F. the rate of adequateprehydrogenation is slow, but may be achieved by a residence time ofseveral hours. At the higher temperatures of about 950F.prehdyrogenation occurs in a few minutes. The criteria of adequateprehydrogenation is the ultimate increased recovery of organic matterfrom the shale which is expressed most conveniently in terms of organiccarbon recovery. By the process of this invention, as much as aboutpercent of the organic carbon can be removed from oil shale in the formof valuable liquid and gaseous hydrocarbons. Longer residence times atthe higher temperatures lead to undesired production of oil and gas byhydroretorting in the preheat and prehydrogenation zone. It is desiredto limit oil production in the preheat and prehydrogenation zone toavoid plugging of the shale in this zone. It is desired not to producesubstantial quantities of hydrocarbons in the preheat andprehydrogenation zone, preferably less than about 15 to 20 weightpercent of the organic component of the shale is converted to normallyliquid or gaseous hydrocarbons. It is especially preferred to convertless than about 10 weight percent of the organic component of the shaleto liquid or gas in this zone.

The terminology hydrogen-rich gas throughout this description andclaims, means gases with sufficient hydrogen partial pressure to effecthigh organic carbon recovery from the organic material in the oilshales. Such hydrogenrich gases may be obtained by a number of processeswell known in the chemical process industry. Table I shows the effect ofthe hydrogen partial pressure and the heatup rate upon organic carbonrecovery from prehydrogenated oil shales which had an original organiccarbon content of 2 l .1 weight percent. The maximum temperature towhich the shale was heated was 1 150F.

TABLE 1 Percent Organic Carbon Recovery Table I shows that hydrogen-richgases of 35 psia hydrogen partial pressure are suitable for use in thisinvention. It is preferred to use hydrogen-rich gas having a partialpressure of hydrogen greater than about I psia. The upper operatingpressures are limited only by equipment and economic considerations. Onebenefit of the higher hydrogen partial pressure is that it allows higherrates hence, less residence time and smaller reactors. Total operatingpressures throughout the system are usually substantially the same.Normally the process of this invention may be carried out at totalpressures of about 40 to about 1500 psia, preferably about 500 to 1000psia.

It is preferred that the oil shale not be thermally shocked by abrupttemperature changes, but that it be gradually heated at a rate in theorder of less than about 100F. per minute. It is preferred that theheating rate be less than about 50F. per minute.

The oil shale and hydrogen-rich gas may be heated by external heatingmeans or internal heating means in the preheat and prehydrogenation zoneby a wide variety of methods which are readily apparent to one skilledin the art. Such variety of heating means allow both cocurrent andcountercurrent operation of the preheat and prehydrogenation zone withrespect to the shale and hydrogen-rich gas. One method which ispreferred is the introduction of oil shale at ambient temperatures atone end of the preheat and prehydrogenation zone and the introduction ofthe hydrogen-rich gas at the other end of the preheat andprehydrogenation zone at a temperature in quantities sufficient to heatthe oil shale to about 700 to about 950F. by countercurrent flow of thehydrogen-rich gas in thermal exchange rela- 4 tion to the oil shales. Tomaximize the production of aliphatic and alicyclic hydrocarbon liquidsfrom the oil shales, it can be seen from Table I that the preferredpartial pressure of hydrogen at its introduction to the preheat andprehydrogenation zone should be about psia, or greater.

The preheated and prehydrogenated oil shale is destructively distilledin a hydroretort zone at a temperature of about 850 to about 1250F. inthe presence of hydrogen-rich gas to form aliphatic and alicyclichydrocarbon liquids and low molecular weight paraffinic hydrocarbongases from the preheated and prehydrogenated organic portion of the oilshales. It is necessary to reach a temperature of about 850F. in orderot obtain the desired hydroretorting in a reasonable period of time. Itis desired, in order to obtain the maximum yield of aliphatic andalicyclic hydrocarbon liquids and low molecular weight paraffinichydrocarbon gases, to maintain the temperature in the hydroretort zoneat lower than about I250F. The maintenance of the temperature in thehydroretort zone at lower than about I250F. limits the inorganiccarbonate decomposition to acceptable levels and also limits thedestructive hydrogenation of organic matter to gaseous paraffinichydrocarbons called hydro gasification, in the hydroretort zone.Formation of carbon dioxide by inorganic carbonate decomposition in thehydroretort zone is undesirable due to its direct dilution of thehydrogen-rich gas, its consumption of hydrogen in conversion to carbonmonoxide and steam, and its use of heat for decomposition. Therefore, ifpipeline-quality gas is desired, additional purification is required toremove the carbon dioxide and carbon monoxide so formed.

Table II shows the effect of temperature in the hydroretort zone uponthe decomposition of mineral carbonate under conditions wherein the oilshale was heated at a rate of 33F. per minute and the original mineralcarbonate content of the oil shale was 12.54 weight percent.

Hydrogasification in the hydroretort zone is not necessarily detrimentalif the desired product is only fuel gas. At higher temperatures thanabout I250F., in-

creasing proportions of paraffinic hydrocarbon gases are formed whichare the most valuable constituents of fuel gases and are the onlyacceptable major constituents of pipeline-quality gas. However, attemperatures above about 1250F. the yield of liquid hydrocarbons beginsto decrease substantially and the liquids which are produced becomeincreasingly aromatic in composition. The data showing productdistribution and organic carbon recovery are illustrated in Table IIIfor a typical heat-up rate and hydrogen partial pressure in laboratorywork simulating the combined results of the preheating, prehydrogenationand hydroretorting steps. Eventually, as temperatures are increasedfurther, the total organic carbon recovery drops to unacceptable levelsbecause of coke and carbon formation of the organic component of the oilshale.

TABLE III Liquid Product Properties l.B.P.-400F. Distillate Fraction(percent) Maximum Average Hydrogen l.B.P.-400F* Aliphatic andTemperature Partial Pressure Percent Organic Carbon Recovery DistillateAlicyclic F. (psia) Total As Gases As Liquids (percent) SaturatedOlcfinie Aromatic 1203 247 90.8 10.7 80.1 3| 28 65 7 I298 252 95.0 50.744.3 36 39 56 MM 236 92.8 63.3 29.5 40 5 35 60 NOTE: *I.B.P.4UUF. showsthe fraction boiling between the initial boiling point and 40()F.

As can be seen from Tables II and III, the maximum hydroretortingtemperature to obtain a combination of low mineral carbonatedecomposition, high total organic carbon recovery and a high proportionof low boiling aliphatic and alicyclic hydrocarbons in the hydrocarbonliquid products, is about l250F. The preferred temperature range isabout 950 to about ll50F. These temperatures vary somewhat over thespecified ranges of hydrogen partial pressure and heatup rate orretention time.

One further consideration which favors hydroretorting at temperaturesnot exceeding about l250F., is that the increase in hydrogasificationreached at the higher temperatures may cause temperature controlproblems since hydrogasification is exothermic.

The hydrogen-rich gas supplied to the hydroretort zone should containsufficient hydrogen to meet the chemical requirements sufficient toconvert the organic portion of the oil shale to aliphatic and alicyclichydrocarbon liquids and paraffinic hydrocarbon gases. It may also bedesirable to add a controlled excess of hydrogen to the hydroretortzone. For example, sufficient excess hydrogen may be added to thehydroretort zone to ultimately convert all of the hydrocarbonsrecovered, and thecarbon monoxide remaining after final purification, tomethane. The use of such an excess of hydrogen in the hydroretort zoneis also a means for providing a portion of the heat necessary to achievethe desired temperatures in the hydroretort zone. However, other heatingmeans may be used and such excess hydrogen may be added at a laterstage. More than such excess of hydrogen, if not separated prior tosubsequent gasification, will only dilute the gaseous products and mayrequire further separation if pipeline-quality gas is desired. Less thansuch excess may lead to undesired carbon deposition if the aliphatic andalicyclic hydrocarbon liquids are subsequently hydrogasified in anotherprocessing step. Lesser than the amounts of hydrogen required chemicallyfor conversion of the prehydrogenated component of oil shale toaliphatic and alicyclic hydrocarbon liquids and low molecular weightparaffinic hydrocarbon gases results in lower organic carbon recovery.

The hydrogen-rich gas may be passed cocurrent or countercurrent to theoil shale in the hydroretort zone. It is preferred to pass thehydrogen-rich gas in cocurrent thermal exchange relation with thepreheated and prehydrogenated shale in the hydroretort zone to avoidcondensation of hydroretorted liquids. The retention time in thehydro-retort zone is sufficient, dependent upon the particulartemperature, pressure and hydrogen concentration in the hydrogen-richgas, to produce by hydroretorting a quantity of aliphatic and alicyclichydrocarbon liquids and low molecular weight gases from the preheatedand prehydrogenated organic components of the oil shale equivalent to atotal organic The hydroretort zone may be heated by any suitable 1method as will be obvious to one skilled in the art. One

method is to supply hydrogen-rich gas of sufficiently high temperatureto raise the temperature of the shale to the desired temperature bydirect thermal exchange. The hydroretort zone may be optionallyinternally heated by any suitable means such as fuel oil/oxygen burner.

Referring to FIG. 1, the fresh oil shale is supplied to preheat andprehydrogenation zone 10 wherein hot hydrogen-rich gas passescountercurrent and in thermal exchange relation to the oil shale at atemperature sufficient to gradually preheat the oil shale to atemperature of about 700 to about 950F. The preheated andprehydrogenated oil shale is then passed to hydroretort zone 11 whereinit is passed cocurrently and in thermal exchange relation withhydrogen-rich gas of sufficient temperature to heat the oil shale to atemperature of about 850 to about 1250F. ln hydroretort zone 11, theorganic component of the oil shale is destructively distilled to formaliphatic and alicyclic hydrocarbon liquids and low molecular weightparaffinic hydrocarbon gases. The aliphatic and alicyclic hydrocarbonliquids, remaining hydrogen-rich gas and any newly formed gaseoushydrocarbons are removed from the hydroretort zone. The aliphatic andalicyclic hydrocarbon liquids may be subjected to further treatment toform other desired products, such as pipeline-quality gas. The spentshale is removed from hydroretort zone 11 and passed through heatrecovery zone 12 in countercurrent and thermal exchange relation tohydrogenrich gas which cools the spent shale to less than about 300F.,preferably to about F. The hydrogen-rich gas is heated in heat recoveryzone 12 for recycle to preheat and prehydrogenation zone 10.

One advantage of the process of this invention is the high thermalefficiency wherein the hydrogen-rich gas may remove a large portion ofthe thermal energy of the spent shale for reutilization in preheating ofthe fresh oil shale. FIG. 1 shows a preferred embodiment of thisinvention wherein hydrogen-rich gas from preheat and prehydrogenationzone 10 passes through separator 13 for removal of liquids, namely waterand hydrocarbon liquids which may be formed in preheat andprehydrogenation zone 10. The organic hydrocarbon liquids from separator13 may be fed into the hydrocar bon liquid output from hydroretort zone11.

The hydrogen-rich gas leaving separator 13 follows a split stream, oneportion recycling to heat recovery zone 12 and another portion supplyinghydroretort zone 11. Valve 17 adjusts the split in the hydrogen-rich gasflow dependent upon the chemical hydrogen requirement in hydroretortzone 11. The hydrogen-rich gas passing from separator 13 to hydroretortzone 11 may be heated by any suitable heating means shown as 15, priorto introduction to hydroretort zone 11. Alternatively, the hydrogen-richgas may be supplied directly to the hydroretort zone 11 withoutpreheating and hydroretort zone 11 may be heated by any suitable meansshown in FIG. 1 as heat input means 16. Heat input means 16 may becombustion of fuel with oxygen.

The other portion of the stream of hydrogen-rich gas from separator 13is recycled to heat recovery zone 12. The amount of hydrogen-rich gasmakeup is determined by the amount of hydrogen consumed in theprehydrogenation and hydroretort zones and discharged from hydroretortzone 11. The hydrogen-rich gas is heated in heat recovery zone 12 andupon passing from heat recovery zone 12 may be further heated by anysuitable heater means 14 prior to introduction to preheat andprehydrogenation zone to obtain the desired temperature for entry topreheat and prehydrogenation zone 10. It is seen from FIG. 1 that alarger volume of hydrogen-rich gas passes through preheat andprehydrogenation zone 10 then passes through hydroretort zone 11.

The advantages of the process of this invention appear to be achieved bythe controlled gradual preheating and prehydrogenation in zone 10followed by higher temperature hydroretorting of the preheated andprehydrogenated oil shale in zone 11. While prior processes of retortingoil shale without gradual preheating and prehydrogenation of the organiccomponent have resulted in less than 80 percent recovery of the organiccarbon from the shale, we have found that with our two-zonehydroretorting process, it is possible to recover as much as about 95percent of the organic carbon from the oil shale.

One important use for the aliphatic and alicyclic hydrocarbon liquidsobtained from the hydroretort zone by the process of this invention, isfor further processing to produce pipeline-quality gas. Pipeline-qualitygas may be obtained from such readily gasifiable liquids by any suitablemethod of producing a methane-rich gas. The aliphatic and alicyclichydrocarbon liquids may be further treated to produce pipeline-qualitygas by many known. processes including hydrogasification by gas recyclehydrogenation or fluidized bed hydrogenation, naphtha reforming,catalytic-rich gas, methane-rich gas or Lurgi Gasynthan processes.

FIG. 2 illustrates a preferred embodiment of this invention in theproduction of pipeline-quality gas. Aliphatic and alicyclic hydrocarbonliquids are produced in generally the same manner as previouslydescribed with further increases in thermal efficiency of the processbeing obtained by recovery of some hydrogen-rich gas recycle from theproduct of hydroretort zone 11 and by utilization of heat from a heatexchanger cooling the gas output of a hydrogasifier to heat hydrogenrichgas input to hydroretort zone 11.

In the embodiment shown in FIG. 2, the effluent stream of hydroretortzone 11 is passed through cooler 30 and liquid-gas separator 31 toseparate the hydrocarbon liquids from hydrogen-rich gas. A portion ofthe hydrogen-rich gas so separated may then be recycled to hydroretortzone 11 through control valve 38. Any hydrogen-rich gas not necessary inhydrogasifier 33 may be recycled in this manner. The hydrocarbon liquidoutput from liquid-gas separator 31 is passed to fractionator 32 whichseparates high boiling hydrocarbon liquids from the low boilinghydrocarbon liquids, thereby obtaining the preferred C/H ratio of about7/1 prior to hydrogasification. The high boiling liquids may be used asfuel to supply heat to the process or as feed to produce hydrogenmake-up gas. The low boiling hydrocarbon liquids from fractionator 32are then fed through a convention hydrogasifier shown as 33 which isusually maintained at a temperature of about 1200 to about l500F. andsuitable pressure to effect gasification. The effluent gas fromhydrogasifier 33 is passed through heat exchanger 34 wherein thehydrogen-rich gas passing to hydroretort zone 11 may be heated bythermal exchange with the hydrogasified gas. The cooled by hydrogasifiedgas is then passed through a condenser-cooler removing water, benzene,toluene, xylene followed by purification to remove any remainingquantities of undesired steam, carbon monoxide carbon dioxide, hydrogensulfide, and nitrogen. Following such purification, the hydrogasifiedproduct is methanated in a conventional manner to increase the amount ofmethane in the resulting pipeline-quality gas.

The combination of the hydrogasifier process with the process forproduction of hydrocarbon liquids and gases from oil shale results inhigh overall thermal efficiency.

Suitable apparatus for use in the process of this invention will bereadily apparent to one skilled in the art. It is apparent that theprocess of this invention may be operated in a physically separatedpreheat and prehydrogenation zone and hydroretort zone or the preheatand prehydrogenation zone and the hydroretort zone may be physicallycontained in one vessel appropriately separated. When operated on abatch basis, the preheat and prehydrogenation conditions may first besubjected to a single zone to which same zone the hydroretort conditionsare later applied. It is readily apparent the process of this inventionmay be carried out on either a batch or continuous flow basis. Acontinuous flow process is preferred.

While no specific means of distribution of the hydrogen-rich gasthroughout the zones containing oil shale is shown, it is readilyapparent that it is desirable to have a suitable gas distribution meanssuch as a gas manifold distribution system at the introduction area ofthe gas to the particular zone. The desirable factor is that thehydrogen-rich gas be effectively distributed to the cross-sectional areaof the zone upon its introduction or shortly thereafter.

Suitable materials for construction of an apparatus suitable for theprocess of this invention are well known to persons skilled in the artand need only be sufficient to contain the pressures obtained in theprocess and to effect suitable heat retentions in the different thermalzones of the process of this invention.

EXAMPLE I Oil shale having a Fischer Assay of 24 gallons per ton wascrushed into particles of about one-half inch in size. The crushedshale, at ambient temperature of about 77F.,-was introduced into avessel having an upper preheat and prehydrogenation zone, a hydroretortzone in the middle and a heat recovery zone 9 in the lower portion.These zones are separated by two decks, one between the bottom of thepreheat and prehydrogenation zone and the top of the hydroretort zoneand the other between the bottom of the hydroretort zone and the top ofthe heat recovery zone. Solid flow by gravity through these zones wascontrolled by a solids flow controller at the spent shale exit in thebottom of the heat recovery zone. The entire system operated at a totalpressure of 1000 psia and lock hoppers were used to introduce thecrushed shale to the upper end of the preheat and prehydrogenation zoneand moved through this zone countercurrent to hydrogen-rich gas.Hydrogen-rich gas containing 93.9 mol percent hydrogen was introduced ata rate of 4.3 mols/hr. at a temperature of 950 F. to the bottom of thepreheat and prehydrogenation zone through a gas distributor. The shalewas introduced at the rate of 100 pounds per hour for a residence timeof about 15 minutes flowing countercurrent to the hydrogen-rich gas. Theshale left the preheat and prehydrogenation zone at a temperature of850F. and entered directly to the top of the hydroretort zone. About 0.6pounds per hour of hydrocarbon oils having a carbon/hydrogen ratio of6.95/1 and about 0.34 pounds per hour of water were formed in thepreheat and prehydrogenation zone. The oil and water were removed fromthe hydrogen-rich gas leaving the top of the preheat andprehydrogenation zone and the oil was fed directly to a gas phasehydrogasifier.

The shale was further heated in the hydroretort zone to 1l00F. by acombination of cocurrent flow with hydrogen-rich gas introduced to thetop of the hydroretort zone at 1350F. and by direct firing of fuel andoxygen within the zone. 0.12 pound per hour of the aromatic liquidsproduced in the gas phase hydrogasifier were used as fuel for thispurpose. 0.5 mols/hr. of gas containing hydrogen were supplied to morethan satisfy the chemical requirements for complete hydroretorting. Thisgas was removed from the top of the preheat and prehydrogenation zoneand after liquids removed, was heated to 1350F. and introduced to thetop of the hydroretort zone. The residence time of the shale in thehydroretort zone was about 5 minutes. The output of the hydroretort zoneshowed that 90.8 percent of the organic carbon in the shale had beenconverted, 82.7 percent to hydrocarbon liquids having a C/H ratio of7.4/1 and 8.1 percent to low molecular weight paraffinic hydrocarbongases.

The spent shale was removed from the bottom of the hydroretort zone tothe top of the heat recovery zone wherein it was cooled to 150F. bycountercurrent flow with hydrogen-rich gas recycled from the preheat andprehydrogenation zone. 3.8 mols per hour of gas containing 93.8 molpercent hydrogen were recycled from the preheat and prehydrogenationzone at 100F., heated to 792F. in the heat recovery zone and furtherheated to 950F. by a furnace in the recycle line bypassing thehydroretort zone and fed to the bottom of the preheat andprehydrogenation zone. 0.51 mols/hr. of 94.4 percent hydrogen-richmake-up gas was added to the hydrogen-rich gas fed to the bottom of theheat recovery zone. 10.3 pounds per hour of hydrocarbon liquids from thehydroretort zone and 1.2 pounds per hour of water were separated fromthe product gases by cooling. The hydrocarbon liquids were thenfractionated and the low boiling hydrocarbon fraction produced at therate of 4.2 pounds per hour and having a C/H ratio of 7.0/1 were fed,together with the product gases from the separator, to a recycle typegas phase hydrogasifier operated at 1400F. Hydrocarbons having a C/l-lratio of 7.0/1 or less limit the carbon deposition in the hydrogasifier.The high boiling hydrocarbon fraction produced at the rate of 6.0 poundsper hour and having a C/l-l ratio of 7.7/1 were fed to a partialoxidation plant for producing hydrogen-rich gas make-up for use in theprocess. The product of the hydrogasifier at 1400F. was passed inthermal exchange relation with the hydrogen-rich gas removed from thetop of the preheat and prehydrogenation zone prior to its introductionto the top of the hydroretort zone, heating such hydrogen-rich gas fromF. to 1350F. and cooling the product of the hydro gasifier to 720F.After passing through this heat exchanger, the gaseous product wasfurther cooled and 0.034 pounds per hour of water and 0.73 pounds perhour of aromatic liquids were removed. Then 0.012 mols per hour ofcarbon dioxide and 0.010 mols per hour of hydrogen sulfide were removedand the gas methanated resulting in dried pipeline-quality gas having agross heating value of 951 BTU/SCF and containing less than 0.1 percentcarbon monoxide. 1.58 SCF of pipeline-quality gas containing 92.8 molpercent methane was produced per pound of dry shale.

While in the foregoing specification this invention has been describedin relation to certain preferred embodiments thereof, and many detailshave been set forth for purpose of illustration, it will be apparent tothose skilled in the art that the invention is susceptible to additionalembodiments and that certain of the details described herein can bevaried considerably without departing from the basic principles of theinvention.

We claim:

1. A process for the production of aliphatic and alicyclic hydrocarbonliquids from oil shale wherein above about 77 percent of the organiccarbon in said oil shale is converted to said liquids and gasescomprising the steps:

introducing fresh oil shale into a preheat and prehydrogenation zone;

gradually preheating, at a rate of less than about 100F. per minute, oilshale in the preheat and prehydrogenation zone to a temperature of about700 to about 950F. in the presence of hydrogenrich gas with less thanabout 20 weight percent of the organic component of oil shale convertedto' liquid and gas in said preheat and prehydrogenation zone, saidhydrogen-rich gas and shale passing countercurrently in said zone;destructively distilling the preheated and prehydrogenated oil shale ina hydroretort zone at a temperature of about 850 to about 1250F. in thepresence of at least a stoichiometric amount of hydrogen-rich gas toform aliphatic and alicyclic hydrocarbon liquids and low molecularweight paraffinic hydrocarbon gases from the preheated andprehydrogenated organic portion of said oil shale; and

said hydrogen-rich gas being supplied to said preheat andprehydrogenation zone in larger volumes than the hydrogen-rich gassupplied to said hydroretort zone.

2. The process of claim 1 wherein spent shale is passed from saidhydroretort zone to a heat recovery zone wherein hydrogen-rich gasrecycled from said preheat and prehydrogenation zone passescountercurrent and in thermal exchange relation to said spent shale 1 lcooling the spent shale and heating the hydrogen-rich gas forintroduction to said preheat and prehydrogenation zone.

3. The process of claim 2 wherein hydrogen-rich gas make-up is added tosaid hydrogen-rich gas recycle prior to introduction to said heatrecovery zone.

4. The process of claim 2 wherein hydrogen-rich gas make-up is added tosaid heat recovery zone.

5. The process of claim 2 wherein said heated hydrogen-rich gas isfurther heated during passage from said heat recovery zone to saidpreheat and prehydrogenation zone.

6. The process of claim 2 wherein the hydrogen-rich gas recycle ispassed through a liquid separator after leaving the preheat andprehydrogenation zone and prior to the addition of hydrogen-rich gasmake-up.

7. The process of claim 2 wherein the hydrogen-rich gas stream leavingsaid preheat and prehydrogenation zone is split with one portion.containing sufficient gas to provide at least the chemical hydrogenrequirements in the hydroretort zone, is passed to said hydroretort zoneand the other portion is recycled to said heat recovery zone.

8. The process of claim 7 wherein said one portion of hydrogen-gasstream is further heated during passage to said hydroretort zone.

9. The process of claim 1 wherein the oil shale is preheated to about750 to about 850F. in said preheat and prehydrogenation zone.

10. The process of claim 1 wherein said preheated and prehydrogenatedoil shale is passed through said hydroretort zone in cocurrent thermalexchange relation with said hydrogen-rich gas.

11. The process of claim 1 wherein the preheated and prehydrogenated oilshale is heated to about 950 to about ll50F. in said hydroretort zone.

12. The process of claim 11 wherein the preheated and prehydrogenatedshale in the retort zone is heated by an internal heating means.

13. The process of claim 1 wherein the preheat and prehydrogenation zoneand the hydroretort zone is at a total gas pressure of about 40 to about1500 psiz.

14. The process of claim 13 wherein the hydrogen partial pressure isgreater than about 100 psia.

15. The process of claim 1 wherein hydrogen-rich gas is separated fromthe aliphatic and alicyclic hydrocarbon liquids formed in saidhydroretort zone and recycled to said hydroretort zone.

16. The process of claim 1 1 wherein more than about percent of theorganic portion of oil shale is converted to liquid.

17. The process of claim 1 wherein above about percent of the organiccarbon in said oil shale is converted to said liquids and gases.

18. The process of claim 1 wherein said aliphatic and alicyclic liquidsare gasified in a hydrogasifier and wherein the hydrogen-rich gasprovided to said hydroretort zone is heated by thermal exchange with theoutput stream of said hydrogasifier.

1. A PROCESS FOR THE PRODUCTION OF ALIPHATIC AND ALICYCLIC HYDROCARBONLIQUIDS FROM OIL SHALE WHEREIN ABOVE ABOUT 77 PERCENT OF THE ORGANICCARBON IN SAID OIL SHALE IS CONVERTED TO SAID LIQUIDS AND GASESCOMPRISING THE STEPS; INTRODUCING FRESH OIL SHALE INTO A PREHEAT ANDPREHYDROGENATION ZONE; GRADUALLY PREHEATING AT A RATE OF LESS THAN ABOUT100:F. PER MINUTE, OIL SHALE IN THE PREHEAT AND PREHYDROGENATION ZONE TOA TEMPERATURE OF ABOUT 700* TO ABOUT 950*F. IN THE PRESENCE OFHYDROGEN-RICH GAS WITH LESS THAN ABOUT 20 WEIGHT PERCENT OF THE ORGANICCOMPONENT OF OIL SHALE CONVERTED TO LIQUID AND GAS IN SAID PREHEAT ANDPREHYDROGENATION ZONE, SAID HYDROGEN-RICH GAS AND SHALE PASSINGCOUNTERCURRENTLY IN SAID ZONE; DESTRICTIVELY DISTILLING THE PREHEATEDAND PREHYDROGENATED OIL SHALE IN A HYDRORETORT ZONE AT A TEMPERATURE OFABOUT 850* TI ABOUT 1250*F. IN THE PRESENCE OF AT LEAST A STOICHIOMETRICAMOUNT OF HYDROGEN-RICH GAS TO FORM ALIPHATIC
 2. The process of claim 1wherein spent shale is passed from said hydroretort zone to a heatrecovery zone wherein hydrogen-rich gas recycled from said preheat andprehydrogenation zone passes countercurrent and in thermal exchangerelation to said spent shale cooling the spent shale and heating thehydrogen-rich gas for introduction to said preheat and prehydrogenationzone.
 3. The process of claim 2 wherein hydrogen-rich gas make-up isadded to said hydrogen-rich gas recycle prior to introduction to saidheat recovery zone.
 4. The process of claim 2 wherein hydrogen-rich gasmake-up is added to said heat recovery zone.
 5. The process of claim 2wherein said heated hydrogen-rich gas is further heated during passagefrom said heat recovery zone to said preheat and prehydrogenation zone.6. The process of claim 2 wherein the hydrogen-rich gas recycle ispassed through a liquid separator after leaving the preheat andprehydrogenation zone and prior to the addition of hydrogen-rich gasmake-up.
 7. The process of claim 2 wherein the hydrogen-rich gas streamleaving said preheat and prehydrogenation zone is split with oneportion, containing sufficient gas to provide at least the chemicalhydrogen requirements in the hydroretort zone, is passed to saidhydroretort zone and the other portion is recycled to said heat recoveryzone.
 8. The process of claim 7 wherein said one portion of hydrogen-gasstream is further heated during passage to said hydroretort zone.
 9. Theprocess of claim 1 wherein the oil shale is preheated to about 750* toabout 850*F. in said preheat and prehydrogenation zone.
 10. The processof claim 1 wherein said preheated and prehydrogenated oil shale ispassed through said hydroretort zone in cocurrent thermal exchangerelation with said hydrogen-rich gas.
 11. The process of claim 1 whereinthe preheated and prehydrogenated oil shale is heated to about 950* toabout 1150*F. in said hydroretort zone.
 12. The process of claim 11wherein the preheated and prehydrogenated shale in the retort zone isheated by an internal heating means.
 13. The process of claim 1 whereinthe preheat and prehydrogenation zone and the hydroretort zone is at atotal gas pressure of about 40 to about 1500 psiz.
 14. The process ofclaim 13 wherein the hydrogen partial pressure is greater than about 100psia.
 15. The process of claim 1 wherein hydrogen-rich gas is separatedfrom the aliphatic and alicyclic hydrocarbon liquids formed in saidhydroretort zone and recycled to said hydroretort zone.
 16. The processof claim 11 wherein more than about 80 percent of the organic portion ofoil shale is converted to liquid.
 17. The process of claim 1 whereinabove about 85 percent of the organic carbon in said oil shale isconverted to said liquids and gases.
 18. The process of claim 1 whereinsaid aliphatic and alicyclic liquids are gasified in a hydrogasifier Andwherein the hydrogen-rich gas provided to said hydroretort zone isheated by thermal exchange with the output stream of said hydrogasifier.